This invention relates to indexing mechanisms and more particularly, it concerns a novel driving and latching mechanism for indexing multi-position control elements, such as programming cams used in automated equipment for performing any one of several operational cycles in accordance with information provided by an indexed position of such cams.
Various types of automated equipment are often programmed to any one of several operational modes for the performance of selected or sequential functions in accordance with information supplied by a programming device indexible to multiple positions corresponding to the respective modes in which the equipment may be operated. As an example of such equipment, reference is made to cassette contained motion picture film strip handling equipment of the type disclosed in U.S. Pat. No. 3,941,465 issued Mar. 2, 1976 to Irwin E. Figge, et al. Such apparatus is designed to receive a self-contained multi-function film cassette and to be programmed either to project, process exposed but unprocessed film, or merely to condition the apparatus in an off position to receive subsequent film cassettes. The manner in which the various viewer mounted components are operated to function with the film cassette is conveniently determined by a rotatably indexed programming cam to control the operational mode to which the viewer is conditioned.
Because of the several control functions served by the programming cam of such equipment in each of the respective indexed positions thereof, it is important that the cam be positively latched after it is rotated from a previous position. It is also important that the time required for indexing be minimized inasmuch as such indexing time is actually a delay in the operation of the equipment when the program of operation is changed.
The torque necessary to drive a rotatable programming cam between successive indexed positions is desirably provided by a drive motor connected to other operating components in the equipment. The use of such drive motor torque thus requires a facility for coupling and decoupling the drive motor with the logic disc in addition to the latching function mentioned above. In addition, and particularly in the motion picture film strip viewing equipment referred to, in which a programming cam is indexed to three programming positions such as "Off", "Project", and "Process/Rewind", a facility for rotating the cam past the off position or between project and rewind without changing the direction of cam indexing movement is desirable from the standpoint of a replay capability. Cam indexing mechanisms which have provided this facility in the past have been complicated, expensive and of doubtful reliability.